Slack's letter adopts the tortured conceit that it will give Microsoft advice about how to build a team-communication app. This puts the company in the odd position of having to pretend it is not just rooting for a competitor but offering material support. "We’re genuinely excited to have some competition," it begins — "genuinely" not being a word we usually feel the need to add when we’re being genuine. But soon the letter's actual point, which is to anxiously brag about Slack, peeks through the clouds. "All this is harder than it looks," Slack warns. And then the company straps on its wax wings and flies into the sun.